Re: markup-command rounded-box is broken

[Lukas-Fabian Moser]

Hi Harm,

> I noticed a bug with recent master:
>
> \markup \rounded-box "foo"
>
> prints completely black.
>
> First bad commit is:
> commit 0772e38398972d6c2b4ba9e6f42e7725d973e08b
> Author: Han-Wen Nienhuys <hanwenn@gmail.com>
> Date:   Sun Aug 1 11:15:02 2021 +0200
>
>      Stop passing color names to output backends

Well, comparing that version pre- and post-change

 (define-public (rounded-box-stencil stencil thickness padding blot)
   "Add a rounded box around @var{stencil}, producing a new stencil."

   (let* ((xext (interval-widen (ly:stencil-extent stencil 0) padding))
          (yext (interval-widen (ly:stencil-extent stencil 1) padding))
          (min-ext (min (-(cdr xext) (car xext)) (-(cdr yext) (car yext))))
          (ideal-blot (min blot (/ min-ext 2)))
          (ideal-thickness (min thickness (/ min-ext 2)))
          (outer (ly:round-filled-box
                  (interval-widen xext ideal-thickness)
                  (interval-widen yext ideal-thickness)
                  ideal-blot))
-         (inner (ly:make-stencil (list 'color (x11-color 'white)
-                                       (ly:stencil-expr 
(ly:round-filled-box
-                                                         xext yext (- 
ideal-blot ideal-thickness)))))))
+         (inner (ly:make-stencil (ly:stencil-in-color
+                                  (ly:round-filled-box
+                                   xext yext (- ideal-blot 
ideal-thickness))
+                                   "white"))))
     (set! stencil (ly:stencil-add outer inner))
     stencil))

it seems to me that before Han-Wen's change, ly:make-stencil was 
necessary since the code manipulated the stencil expression of the 
round-filled-box directly, thus returning a stencil expression. Now, 
with the use of ly:stencil-in-color, we get an actual stencil 
immediately, so the call ly:make-stencil (which expects a stencil 
expression) is superfluous and (I think) wrong.

But to be honest, rounded-box-stencil seems to me to be broken anyway:

If you compare it with ellipse-stencil directly above (and looking at 
the docstrings), one should expect to get the original stencil with an 
added rounded box. But rounded-box-stencil
a) doesn't use the original stencil in stencil-add,
b) overwrites the original stencil with set!

Hence, the markup command \rounded-box has to take care to add the 
original markup:

  (let ((th (* (ly:output-def-lookup layout 'line-thickness)
               thickness))
        (pad (* (magstep font-size) box-padding))
        (m (interpret-markup layout props arg)))
    (ly:stencil-add (rounded-box-stencil m th pad corner-radius)
                    m)))

So in my impression, rounded-box-stencil might deserve a refactoring anyway?

Lukas